Learn for knowledge.... (Hamim Ali Aakash)

"Who invented the computer?" is not a question with a simple answer. The real answer is that many inventors contributed to the history of computers and that a computer is a complex piece of machinery made up of many parts, each of which can be considered a separate invention.

This series covers many of the major milestones in computer history (but not all of them) with a concentration on the history of personal home computers.

Computer History Year/Enter	Computer History Inventors/Inventions	Computer History Description of Event
1936	Konrad Zuse - Z1 Computer	First freely programmable computer.
1942	John Atanasoff & Clifford Berry ABC Computer	Who was first in the computing biz is not always as easy as ABC.
1944	Howard Aiken & Grace Hopper Harvard Mark I Computer	The Harvard Mark 1 computer.
1946	John Presper Eckert & John W. Mauchly ENIAC 1 Computer	20,000 vacuum tubes later...
1948	Frederic Williams & Tom Kilburn Manchester Baby Computer & The Williams Tube	Baby and the Williams Tube turn on the memories.
1947/48	John Bardeen, Walter Brattain & Wiliam Shockley The Transistor	No, a transistor is not a computer, but this invention greatly affected the history of computers.
1951	John Presper Eckert & John W. Mauchly UNIVAC Computer	First commercial computer & able to pick presidential winners.
1953	International Business Machines IBM 701 EDPM Computer	IBM enters into 'The History of Computers'.
1954	John Backus & IBM FORTRAN Computer Programming Language	The first successful high level programming language.
1955 (In Use 1959)	Stanford Research Institute, Bank of America, and General Electric ERMA and MICR	The first bank industry computer - also MICR (magnetic ink character recognition) for reading checks.
1958	Jack Kilby & Robert Noyce The Integrated Circuit	Otherwise known as 'The Chip'
1962	Steve Russell & MIT Spacewar Computer Game	The first computer game invented.
1964	Douglas Engelbart Computer Mouse & Windows	Nicknamed the mouse because the tail came out the end.
1969	ARPAnet	The original Internet.
1970	Intel 1103 Computer Memory	The world's first available dynamic RAM chip.
1971	Faggin, Hoff & Mazor Intel 4004 Computer Microprocessor	The first microprocessor.
1971	Alan Shugart &IBM The "Floppy" Disk	Nicknamed the "Floppy" for its flexibility.
1973	Robert Metcalfe & Xerox The Ethernet Computer Networking	Networking.
1974/75	Scelbi & Mark-8 Altair & IBM 5100 Computers	The first consumer computers.
1976/77	Apple I, II & TRS-80 & Commodore Pet Computers	More first consumer computers.
1978	Dan Bricklin & Bob Frankston VisiCalc Spreadsheet Software	Any product that pays for itself in two weeks is a surefire winner.
1979	Seymour Rubenstein & Rob Barnaby WordStar Software	Word Processors.
1981	IBM The IBM PC - Home Computer	From an "Acorn" grows a personal computer revolution
1981	Microsoft MS-DOS Computer Operating System	From "Quick And Dirty" comes the operating system of the century.
1983	Apple Lisa Computer	The first home computer with a GUI, graphical user interface.
1984	Apple Macintosh Computer	The more affordable home computer with a GUI.
1985	Microsoft Windows	Microsoft begins the friendly war with Apple.

History of computer...............

Prehistoric man did not have the Internet, but it appears that he needed a way to count and make calculations. The limitations of the human body’s ten fingers and ten toes apparently caused early man to construct a tool to help with those calculations. Scientists now know that humankind invented an early form of computers. Their clue was a bone carved with prime numbers found in 8,500 BC.

The abacus was the next leap forward in computing between 1000 BC and 500 BD. This apparatus used a series of moveable beads or rocks. The positions changed to enter a number and again to perform mathematical operations. Leonardo DaVinci was credited with the invention of the world’s first mechanical calculator in 1500. In 1642, Blaise Pascal’s adding machine upstaged DaVinci’s marvel and moved computing forward again.

In 19^th century England, Charles Babbage, a mathematician, proposed the construction of a machine that he called the Babbage Difference Engine. It would not only calculate numbers, it would also be capable of printing mathematical tables. The Computer History Museum in Mountain View, CA (near San Diego) built a working replica from the original drawings. Visitors can see in the device in operation there. Unable to construct the actual device, he earned quite a few detractors among England’s literate citizens. However, Babbage made a place for himself in history as the father of computing. Not satisfied with the machines limitations, he drafted plans for the Babbage Analytical Engine. He intended for this computing device to use punch cards as the control mechanism for calculations. This feature would make it possible for his computer to use previously performed calculations in new ones.

Babbage’s idea caught the attention of Ada Byron Lovelace who had an undying passion for math. She also saw possibilities that the Analytical Machine could produce graphics and music. She helped Babbage move his project from idea to reality by documenting how the device would calculate Bernoulli numbers. She later received recognition for writing the world’s first computer program. The United States Department of Defense named a computer language in her honor in 1979.

The computers that followed built on each previous success and improved it. In 1943, the first programmable computer Turing COLOSSUS appeared. It was pressed into service to decipher World War II coded messages from Germany. ENIAC, the brain, was the first electronic computer, in 1946. In 1951, the U.S. Census Bureau became the first government agency to buy a computer, UNIVAC .

The Apple expanded the use of computers to consumers in 1977. The IBM PC for consumers followed closely in 1981, although IBM mainframes were in use by government and corporations.

8,500 BC Bone carved with prime numbers found
1000 BC to 500 BC Abacus invented
1642 Blaise Pascal’s invented adding machine, France
1822 Charles Babbage drafted Babbage Difference Engine, England
1835 Babbage Analytical Engine proposed, England
1843 Ada Byron Lovelace computer program to calculate Bernoulli numbers, England
1943 Turing COLOSSUS the first programmable computer, England
1946 ENIAC first electronic computer, U.S.A.
1951 UNIVAC first computer used by U.S. government, U.S.A.
1969 ARPANET Department of Defense lays groundwork for Internet, U.S.A.
1968 Gordon Moore and Robert Noyce found in Intel, U.S.A.
1977 Apple computers for consumers sold, U.S.A.
1981 IBM personal computers sold, U.S.A.
1991 World Wide Web consumer Internet access, CERN, Tim Berners-Lee Switzerland/France
2000 Y 2K Bug programming errors discovered
Current Technologies include word processing, games, email, maps, and streaming

The development of network technology and increases in processing capabilities for microcomputers made consumer Internet use possible by 1991. The computer evolution since then continues. New uses emerge every year.

Computer types

Since the invention of computers from first generation and fourth generation computers, they have been classified according to their types and how they operate that is input, process and output information. Below you will get a brief discussion on various types of Computers we have

Computer types can be divided into 3 categories according to electronic nature. Types of computers are classified according to how a particular Computer functions. These computer types are

· Analogue Computers

· Digital Computers

· Hybrid Computers

Analogue Computers

Analogue types of Computer uses what is known as analogue signals that are represented by a continuous set of varying voltages and are used in scientific research centers?, hospitals and flight centers

With analogue types of computer no values are represented by physical measurable quantities e.g. voltages. Analogue computer types program arithmetic and logical operations by measuring physical changes i.e. temperatures or pressure.

Digital Computer type

With these types of computers operation are on electrical input that can attain two inputs, states of ON=1 and state of OFF = 0. With digital type of computers data is represented by digital of 0 and 1 or off state and on state. Digital computer type recognizes data by counting discrete signal of (0 0r 1), they are high speed programmable; they compute values and stores results. After looking at the Digital computer type and how it functions will move to the third computer type as mentioned above.

Hybrid type of Computer

Hybrid computer types are very unique, in the sense that they combined both analogue and digital features and operations. With Hybrid computers operate by using digital to analogue convertor and analogue to digital convertor. By linking the two types of computer above you come up with this new computer type called Hybrid.

Computer virus(Learn for knowledge)

A computer virus is a computer program that can replicate itself^[1] and spread from one computer to another. The term "virus" is also commonly but erroneously used to refer to other types of malware, including but not limited to adware and spyware programs that do not have the reproductive ability. A true virus can spread from one computer to another (in some form of executable code) when its host is taken to the target computer; for instance because a user sent it over a network or the Internet, or carried it on a removable medium such as a floppy disk,CD, DVD, or USB drive.^[2]

Viruses can increase their chances of spreading to other computers by infecting files on a network file system or a file system that is accessed by another computer.^[3]^[4]

As stated above, the term "computer virus" is sometimes used as a catch-all phrase to include all types of malware, even those that do not have the reproductive ability. Malware includes computer viruses, computer worms, Trojan horses, most rootkits, spyware, dishonest adwareand other malicious and unwanted software, including true viruses. Viruses are sometimes confused with worms and Trojan horses, which are technically different. A worm can exploit security vulnerabilities to spread itself automatically to other computers through networks, while a Trojan horse is a program that appears harmless but hides malicious functions. Worms and Trojan horses, like viruses, may harm a computer system's data or performance. Some viruses and other malware have symptoms noticeable to the computer user, but many are surreptitious or simply do nothing to call attention to themselves. Some viruses do nothing beyond reproducing themselves.

Virus History.....

Academic work

The first academic work on the theory of computer viruses (although the term "computer virus" was not invented at that time) was done in 1949 by John von Neumann who held lectures at the University of Illinois about the "Theory and Organization of Complicated Automata". The work of von Neumann was later published as the "Theory of self-reproducing automata".^[5] In his essay von Neumann postulated that a computer program could reproduce.

In 1972 Veith Risak published his article "Selbstreproduzierende Automaten mit minimaler Informationsübertragung" (Self-reproducing automata with minimal information exchange).^[6] The article describes a fully functional virus written in assembler language for a SIEMENS 4004/35 computer system.

In 1980 Jürgen Kraus wrote his diplom thesis "Selbstreproduktion bei Programmen" (Self-reproduction of programs) at the University of Dortmund.^[7] In his work Kraus postulated that computer programs can behave in a way similar to biological viruses.

In 1984 Fred Cohen from the University of Southern California wrote his paper "Computer Viruses - Theory and Experiments".^[8] It was the first paper to explicitly call a self-reproducing program a "virus", a term introduced by Cohen's mentor Leonard Adleman.

An article that describes "useful virus functionalities" was published by J. B. Gunn under the title "Use of virus functions to provide a virtual APL interpreter under user control" in 1984.^[9]

Science fiction

The actual term "virus" was first used to denote a self-reproducing program in a short story by David Gerrold in Galaxy magazine in 1969 - and later in his 1972 novel, When HARLIE Was One. In that novel, a sentient computer named HARLIE writes viral software to retrieve damaging personal information from other computers to blackmail the man who wants to turn him off.

The Terminal Man, a science fiction novel by Michael Crichton (1972), told (as a sideline story) of a computer with telephone modem dialing capability, which had been programmed to randomly dial phone numbers until it hit a modem that is answered by another computer. It then attempted to program the answering computer with its own program, so that the second computer would also begin dialing random numbers, in search of yet another computer to program. The program is assumed to spread exponentially through susceptible computers.

Virus programs

The Creeper virus was first detected on ARPANET, the forerunner of the Internet, in the early 1970s.^[10] Creeper was an experimental self-replicating program written by Bob Thomas at BBN Technologies in 1971.^[11] Creeper used the ARPANET to infect DEC PDP-10 computers running the TENEX operating system.^[12] Creeper gained access via the ARPANET and copied itself to the remote system where the message, "I'm the creeper, catch me if you can!" was displayed. The Reaper program was created to delete Creeper.^[13]

A program called "Elk Cloner" was the first computer virus to appear "in the wild"—that is, outside the single computer or lab where it was created.^[14] Written in 1981 by Richard Skrenta, it attached itself to the Apple DOS 3.3 operating system and spread via floppy disk.^[14]^[15]This virus, created as a practical joke when Skrenta was still in high school, was injected in a game on a floppy disk. On its 50th use the Elk Cloner virus would be activated, infecting the computer and displaying a short poem beginning "Elk Cloner: The program with a personality."

The first PC virus in the wild was a boot sector virus dubbed (c)Brain,^[16] created in 1986 by the Farooq Alvi Brothers in Lahore, Pakistan, reportedly to deter piracy of the software they had written.^[17]

Before computer networks became widespread, most viruses spread on removable media, particularly floppy disks. In the early days of thepersonal computer, many users regularly exchanged information and programs on floppies. Some viruses spread by infecting programs stored on these disks, while others installed themselves into the disk boot sector, ensuring that they would be run when the user booted the computer from the disk, usually inadvertently. PCs of the era would attempt to boot first from a floppy if one had been left in the drive. Until floppy disks fell out of use, this was the most successful infection strategy and boot sector viruses were the most common in the wild for many years.^[1]

Traditional computer viruses emerged in the 1980s, driven by the spread of personal computers and the resultant increase in BBS, modemuse, and software sharing. Bulletin board-driven software sharing contributed directly to the spread of Trojan horse programs, and viruses were written to infect popularly traded software. Shareware and bootleg software were equally common vectors for viruses on BBS's.^{[citation needed]}

Macro viruses have become common since the mid-1990s. Most of these viruses are written in the scripting languages for Microsoft programs such as Word and Excel and spread throughout Microsoft Office by infecting documents and spreadsheets. Since Word and Excel were also available for Mac OS, most could also spread to Macintosh computers. Although most of these viruses did not have the ability to send infected email messages, those viruses which did take advantage of the Microsoft Outlook COM interface.^{[citation needed]}

Some old versions of Microsoft Word allow macros to replicate themselves with additional blank lines. If two macro viruses simultaneously infect a document, the combination of the two, if also self-replicating, can appear as a "mating" of the two and would likely be detected as a virus unique from the "parents".^[18]

A virus may also send a web address link as an instant message to all the contacts on an infected machine. If the recipient, thinking the link is from a friend (a trusted source) follows the link to the website, the virus hosted at the site may be able to infect this new computer and continue propagating.

Viruses that spread using cross-site scripting were first reported in 2002,^[19] and were academically demonstrated in 2005.^[20] There have been multiple instances of the cross-site scripting viruses in the wild, exploiting websites such as MySpace and Yahoo.

Infection strategies

In order to replicate itself, a virus must be permitted to execute code and write to memory. For this reason, many viruses attach themselves to executable files that may be part of legitimate programs. If a user attempts to launch an infected program, the virus' code may be executed simultaneously. Viruses can be divided into two types based on their behavior when they are executed. Nonresident viruses immediately search for other hosts that can be infected, infect those targets, and finally transfer control to the application program they infected. Resident viruses do not search for hosts when they are started. Instead, a resident virus loads itself into memory on execution and transfers control to the host program. The virus stays active in the background and infects new hosts when those files are accessed by other programs or the operating system itself.

Nonresident viruses

Nonresident viruses can be thought of as consisting of a finder module and a replication module. The finder module is responsible for finding new files to infect. For each new executable file the finder module encounters, it calls the replication module to infect that file.

Resident viruses

Resident viruses contain a replication module that is similar to the one that is employed by nonresident viruses. This module, however, is not called by a finder module. The virus loads the replication module into memory when it is executed instead and ensures that this module is executed each time the operating system is called to perform a certain operation. The replication module can be called, for example, each time the operating system executes a file. In this case the virus infects every suitable program that is executed on the computer.

Resident viruses are sometimes subdivided into a category of fast infectors and a category of slow infectors. Fast infectors are designed to infect as many files as possible. A fast infector, for instance, can infect every potential host file that is accessed. This poses a special problem when using anti-virus software, since a virus scanner will access every potential host file on a computer when it performs a system-wide scan. If the virus scanner fails to notice that such a virus is present in memory the virus can "piggy-back" on the virus scanner and in this way infect all files that are scanned. Fast infectors rely on their fast infection rate to spread. The disadvantage of this method is that infecting many files may make detection more likely, because the virus may slow down a computer or perform many suspicious actions that can be noticed by anti-virus software. Slow infectors, on the other hand, are designed to infect hosts infrequently. Some slow infectors, for instance, only infect files when they are copied. Slow infectors are designed to avoid detection by limiting their actions: they are less likely to slow down a computer noticeably and will, at most, infrequently trigger anti-virus software that detects suspicious behavior by programs. The slow infector approach, however, does not seem very successful.

More thing about Virus(Learn for knowledge)

Viruses have targeted various types of transmission media or hosts. This list is not exhaustive:

Binary executable files (such as COM files and EXE files in MS-DOS, Portable Executable files in Microsoft Windows, the Mach-O format in OSX, and ELF files in Linux)
Volume Boot Records of floppy disks and hard disk partitions
The master boot record (MBR) of a hard disk
General-purpose script files (such as batch files in MS-DOS and Microsoft Windows, VBScript files, and shell script files on Unix-likeplatforms).
Application-specific script files (such as Telix-scripts)
System specific autorun script files (such as Autorun.inf file needed by Windows to automatically run software stored on USB Memory Storage Devices).
Documents that can contain macros (such as Microsoft Word documents, Microsoft Excel spreadsheets, AmiPro documents, andMicrosoft Access database files)
Cross-site scripting vulnerabilities in web applications (see XSS Worm)
Arbitrary computer files. An exploitable buffer overflow, format string, race condition or other exploitable bug in a program which reads the file could be used to trigger the execution of code hidden within it. Most bugs of this type can be made more difficult to exploit incomputer architectures with protection features such as an execute disable bit and/or address space layout randomization.

PDFs, like HTML, may link to malicious code. PDFs can also be infected with malicious code.

In operating systems that use file extensions to determine program associations (such as Microsoft Windows), the extensions may be hidden from the user by default. This makes it possible to create a file that is of a different type than it appears to the user. For example, an executable may be created named "picture.png.exe", in which the user sees only "picture.png" and therefore assumes that this file is an image and most likely is safe, yet when opened runs the executable on the client machine.

An additional method is to generate the virus code from parts of existing operating system files by using the CRC16/CRC32 data. The initial code can be quite small (tens of bytes) and unpack a fairly large virus. This is analogous to a biological "prion" in the way it works but is vulnerable to signature based detection. This attack has not yet been seen "in the wild".

Methods to avoid detection

In order to avoid detection by users, some viruses employ different kinds of deception. Some old viruses, especially on the MS-DOS platform, make sure that the "last modified" date of a host file stays the same when the file is infected by the virus. This approach does not fool anti-virus software, however, especially those which maintain and date Cyclic redundancy checks on file changes.

Some viruses can infect files without increasing their sizes or damaging the files. They accomplish this by overwriting unused areas of executable files. These are called cavity viruses. For example, the CIH virus, or Chernobyl Virus, infects Portable Executable files. Because those files have many empty gaps, the virus, which was 1 KB in length, did not add to the size of the file.

Some viruses try to avoid detection by killing the tasks associated with antivirus software before it can detect them.

As computers and operating systems grow larger and more complex, old hiding techniques need to be updated or replaced. Defending a computer against viruses may demand that a file system migrate towards detailed and explicit permission for every kind of file access.

Avoiding bait files and other undesirable hosts

A virus needs to infect hosts in order to spread further. In some cases, it might be a bad idea to infect a host program. For example, many anti-virus programs perform an integrity check of their own code. Infecting such programs will therefore increase the likelihood that the virus is detected. For this reason, some viruses are programmed not to infect programs that are known to be part of anti-virus software. Another type of host that viruses sometimes avoid are bait files. Bait files (or goat files) are files that are specially created by anti-virus software, or by anti-virus professionals themselves, to be infected by a virus. These files can be created for various reasons, all of which are related to the detection of the virus:

Anti-virus professionals can use bait files to take a sample of a virus (i.e. a copy of a program file that is infected by the virus). It is more practical to store and exchange a small, infected bait file, than to exchange a large application program that has been infected by the virus.
Anti-virus professionals can use bait files to study the behavior of a virus and evaluate detection methods. This is especially useful when the virus is polymorphic. In this case, the virus can be made to infect a large number of bait files. The infected files can be used to test whether a virus scanner detects all versions of the virus.
Some anti-virus software employs bait files that are accessed regularly. When these files are modified, the anti-virus software warns the user that a virus is probably active on the system.

Since bait files are used to detect the virus, or to make detection possible, a virus can benefit from not infecting them. Viruses typically do this by avoiding suspicious programs, such as small program files or programs that contain certain patterns of 'garbage instructions'.

A related strategy to make baiting difficult is sparse infection. Sometimes, sparse infectors do not infect a host file that would be a suitable candidate for infection in other circumstances. For example, a virus can decide on a random basis whether to infect a file or not, or a virus can only infect host files on particular days of the week.

Stealth

Some viruses try to trick antivirus software by intercepting its requests to the operating system. A virus can hide itself by intercepting the antivirus software’s request to read the file and passing the request to the virus, instead of the OS. The virus can then return an uninfected version of the file to the antivirus software, so that it seems that the file is "clean". Modern antivirus software employs various techniques to counter stealth mechanisms of viruses. The only completely reliable method to avoid stealth is to boot from a medium that is known to be clean.

Self-modification

Most modern antivirus programs try to find virus-patterns inside ordinary programs by scanning them for so-called virus signatures. A signature is a characteristic byte-pattern that is part of a certain virus or family of viruses. If a virus scanner finds such a pattern in a file, it notifies the user that the file is infected. The user can then delete, or (in some cases) "clean" or "heal" the infected file. Some viruses employ techniques that make detection by means of signatures difficult but probably not impossible. These viruses modify their code on each infection. That is, each infected file contains a different variant of the virus.

Encryption with a variable key

A more advanced method is the use of simple encryption to encipher the virus. In this case, the virus consists of a small decrypting module and an encrypted copy of the virus code. If the virus is encrypted with a different key for each infected file, the only part of the virus that remains constant is the decrypting module, which would (for example) be appended to the end. In this case, a virus scanner cannot directly detect the virus using signatures, but it can still detect the decrypting module, which still makes indirect detection of the virus possible. Since these would be symmetric keys, stored on the infected host, it is in fact entirely possible to decrypt the final virus, but this is probably not required, since self-modifying code is such a rarity that it may be reason for virus scanners to at least flag the file as suspicious.

An old, but compact, encryption involves XORing each byte in a virus with a constant, so that the exclusive-or operation had only to be repeated for decryption. It is suspicious for a code to modify itself, so the code to do the encryption/decryption may be part of the signature in many virus definitions.

Polymorphic code

Polymorphic code was the first technique that posed a serious threat to virus scanners. Just like regular encrypted viruses, a polymorphic virus infects files with an encrypted copy of itself, which is decoded by a decryption module. In the case of polymorphic viruses, however, this decryption module is also modified on each infection. A well-written polymorphic virus therefore has no parts which remain identical between infections, making it very difficult to detect directly using signatures. Antivirus software can detect it by decrypting the viruses using an emulator, or by statistical pattern analysis of the encrypted virus body. To enable polymorphic code, the virus has to have a polymorphic engine (also called mutating engine or mutation engine) somewhere in its encrypted body. See Polymorphic code for technical detail on how such engines operate.^[21]

Some viruses employ polymorphic code in a way that constrains the mutation rate of the virus significantly. For example, a virus can be programmed to mutate only slightly over time, or it can be programmed to refrain from mutating when it infects a file on a computer that already contains copies of the virus. The advantage of using such slow polymorphic code is that it makes it more difficult for antivirus professionals to obtain representative samples of the virus, because bait files that are infected in one run will typically contain identical or similar samples of the virus. This will make it more likely that the detection by the virus scanner will be unreliable, and that some instances of the virus may be able to avoid detection.

Metamorphic code

To avoid being detected by emulation, some viruses rewrite themselves completely each time they are to infect new executables. Viruses that utilize this technique are said to be metamorphic. To enable metamorphism, a metamorphic engine is needed. A metamorphic virus is usually very large and complex. For example, W32/Simile consisted of over 14000 lines of Assembly language code, 90% of which is part of the metamorphic engine.^[22]^[23]

Vulnerability and countermeasures

The vulnerability of operating systems to viruses

Just as genetic diversity in a population decreases the chance of a single disease wiping out a population, the diversity of software systems on a network similarly limits the destructive potential of viruses. This became a particular concern in the 1990s, when Microsoft gained market dominance in desktop operating systems and office suites. Microsoft software is targeted by virus writers due to their desktop dominance.

Although Windows is by far the most popular target operating system for virus writers, viruses also exist on other platforms. Any operating system that allows third-party programs to run can theoretically run viruses.

An Internet based experiment revealed that there were cases when people willingly pressed a particular button to download a virus. Security analyst Didier Stevens ran a half year advertising campaign on Google AdWords which said "Is your PC virus-free? Get it infected here!". The result was 409 clicks.^[24]^[25]

As of 2006, there were relatively few security exploits targeting Mac OS X (with a Unix-based file system and kernel).^[26] The number of viruses for the older Apple operating systems, known as Mac OS Classic, varies greatly from source to source, with Apple stating that there are only four known viruses, and independent sources stating there are as many as 63 viruses. Many Mac OS Classic viruses targeted theHyperCard authoring environment. The difference in virus vulnerability between Macs and Windows is a chief selling point, one that Appleuses in their Get a Mac advertising.^[27] In January 2009, Symantec announced the discovery of a trojan that targets Macs.^[28] This discovery did not gain much coverage until April 2009.^[28]

While Linux, and Unix in general, has always natively blocked normal users from having access to make changes to the operating system environment, Windows users are generally not. This difference has continued partly due to the widespread use of administrator accounts in contemporary versions like XP. In 1997, when a virus for Linux was released – known as "Bliss" – leading antivirus vendors issued warnings that Unix-like systems could fall prey to viruses just like Windows.^[29] The Bliss virus may be considered characteristic of viruses – as opposed to worms – on Unix systems. Bliss requires that the user run it explicitly, and it can only infect programs that the user has the access to modify. Unlike Windows users, most Unix users do not log in as an administrator user except to install or configure software; as a result, even if a user ran the virus, it could not harm their operating system. The Bliss virus never became widespread, and remains chiefly a research curiosity. Its creator later posted the source code to Usenet, allowing researchers to see how it worked.^[30]

The role of software development

Because software is often designed with security features to prevent unauthorized use of system resources, many viruses must exploitsoftware bugs in a system or application to spread. Software development strategies that produce large numbers of bugs will generally also produce potential exploits.

Anti-virus software and other preventive measures

Many users install anti-virus software that can detect and eliminate known viruses after the computer downloads or runs the executable. There are two common methods that an anti-virus software application uses to detect viruses. The first, and by far the most common method of virus detection is using a list of virus signature definitions. This works by examining the content of the computer's memory (its RAM, andboot sectors) and the files stored on fixed or removable drives (hard drives, floppy drives), and comparing those files against a database of known virus "signatures". The disadvantage of this detection method is that users are only protected from viruses that pre-date their last virus definition update. The second method is to use a heuristic algorithm to find viruses based on common behaviors. This method has the ability to detect novel viruses that anti-virus security firms have yet to create a signature for.

Some anti-virus programs are able to scan opened files in addition to sent and received email messages "on the fly" in a similar manner. This practice is known as "on-access scanning". Anti-virus software does not change the underlying capability of host software to transmit viruses. Users must update their software regularly to patch security holes. Anti-virus software also needs to be regularly updated in order to recognize the latest threats.

One may also minimize the damage done by viruses by making regular backups of data (and the operating systems) on different media, that are either kept unconnected to the system (most of the time), read-only or not accessible for other reasons, such as using different file systems. This way, if data is lost through a virus, one can start again using the backup (which should preferably be recent).

If a backup session on optical media like CD and DVD is closed, it becomes read-only and can no longer be affected by a virus (so long as a virus or infected file was not copied onto the CD/DVD). Likewise, an operating system on a bootable CD can be used to start the computer if the installed operating systems become unusable. Backups on removable media must be carefully inspected before restoration. The Gammima virus, for example, propagates via removable flash drives.^[31]^[32]

Recovery methods

A number of recovery options exist after a computer has a virus. These actions depend on the virus. Some may be safely removed by functions available in most anti-virus software products. Others may require re-installation of damaged programs. It is necessary to know the characteristics of the virus involved to take the correct action, and anti-virus products will identify known viruses precisely before trying to "dis-infect" a computer; otherwise such action could itself cause a lot of damage. New viruses that anti-virus researchers have not yet studied therefore present an ongoing problem, which requires anti-virus packages to be updated frequently.

Virus removal

One possibility on Windows Me, Windows XP, Windows Vista and Windows 7 is a tool known as System Restore, which restores the registry and critical system files to a previous checkpoint. Often a virus will cause a system to hang, and a subsequent hard reboot will render a system restore point from the same day corrupt. Restore points from previous days should work provided the virus is not designed to corrupt the restore files or also exists in previous restore points.^[33] Some viruses, however, disable System Restore and other important tools such as Task Manager and Command Prompt. An example of a virus that does this is CiaDoor. However, many such viruses can be removed by rebooting the computer, entering Windows safe mode, and then using system tools.

Administrators have the option to disable such tools from limited users for various reasons (for example, to reduce potential damage from and the spread of viruses). A virus can modify the registry to do the same even if the Administrator is controlling the computer; it blocks all users including the administrator from accessing the tools. The message "Task Manager has been disabled by your administrator" may be displayed, even to the administrator.^{[citation needed]}

Users running a Microsoft operating system can access Microsoft's website to run a free scan, provided they have their 20-digit registration number. Many websites run by anti-virus software companies provide free online virus scanning, with limited cleaning facilities (the purpose of the sites is to sell anti-virus products). Some websites allow a single suspicious file to be checked by many antivirus programs in one operation.

Operating system reinstallation

Reinstalling the operating system is another approach to virus removal. It involves either reformatting the computer's hard drive and installing the OS and all programs from original media, or restoring the entire partition with a clean backup image. User data can be restored by booting from a Live CD, or putting the hard drive into another computer and booting from its operating system with great care not to infect the second computer by executing any infected programs on the original drive; and once the system has been restored precautions must be taken to avoid reinfection from a restored executable file.

These methods are simple to do, may be faster than disinfecting a computer, and are guaranteed to remove any malware. If the operating system and programs must be reinstalled from scratch, the time and effort to reinstall, reconfigure, and restore user preferences must be taken into account.

Timeline of Computer History...(Learn for knowledge)...

Computers

1939
David Packard and Bill Hewlett in their Palo Alto, California Garage		Hewlett-Packard is Founded. David Packard and Bill Hewlett found Hewlett-Packard in a Palo Alto, California garage. Their first product was the HP 200A Audio Oscillator, which rapidly becomes a popular piece of test equipment for engineers. Walt Disney Pictures ordered eight of the 200B model to use as sound effects generators for the 1940 movie “Fantasia.”

1940
The Complex Number Calculator (CNC)		The Complex Number Calculator (CNC) is completed. In 1939, Bell Telephone Laboratories completed this calculator, designed by researcher George Stibitz. In 1940, Stibitz demonstrated the CNC at an American Mathematical Society conference held at Dartmouth College. Stibitz stunned the group by performing calculations remotely on the CNC (located in New York City) using a Teletype connected via special telephone lines. This is considered to be the first demonstration of remote access computing.

1941
The Zuse Z3 Computer		Konrad Zuse finishes the Z3 computer. The Z3 was an early computer built by German engineer Konrad Zuse working in complete isolation from developments elsewhere. Using 2,300 relays, the Z3 used floating point binary arithmetic and had a 22-bit word length. The original Z3 was destroyed in a bombing raid of Berlin in late 1943. However, Zuse later supervised a reconstruction of the Z3 in the 1960s which is currently on display at the Deutsches Museum in Munich.


The Bombe at Work		The first Bombe is completed. Based partly on the design of the Polish “Bomba,” a mechanical means of decrypting Nazi military communications during WWII, the British Bombe design was greatly influenced by the work of computer pioneer Alan Turing and others. Many bombes were built. Together they dramatically improved the intelligence gathering and processing capabilities of Allied forces. [Computers]

1942
The Atanasoff-Berry Computer		The Atanasoff-Berry Computer (ABC) is completed. After successfully demonstrating a proof-of-concept prototype in 1939, Atanasoff received funds to build the full-scale machine. Built at Iowa State College (now University), the ABC was designed and built by Professor John Vincent Atanasoff and graduate student Cliff Berry between 1939 and 1942. The ABC was at the center of a patent dispute relating to the invention of the computer, which was resolved in 1973 when it was shown that ENIAC co-designer John Mauchly had come to examine the ABC shortly after it became functional. The legal result was a landmark: Atanasoff was declared the originator of several basic computer ideas, but the computer as a concept was declared un-patentable and thus was freely open to all. This result has been referred to as the "dis-invention of the computer." A full-scale reconstruction of the ABC was completed in 1997 and proved that the ABC machine functioned as Atanasoff had claimed.

1943
Whirlwind installation at MIT		Project Whirlwind begins. During World War II, the U.S. Navy approached the Massachusetts Institute of Technology (MIT) about building a flight simulator to train bomber crews. The team first built a large analog computer, but found it inaccurate and inflexible. After designers saw a demonstration of the ENIAC computer, they decided on building a digital computer. By the time the Whirlwind was completed in 1951, the Navy had lost interest in the project, though the U.S. Air Force would eventually support the project which would influence the design of the SAGE program.


George Stibitz circa 1940		The Relay Interpolator is completed. The U.S. Army asked Bell Labs to design a machine to assist in testing its M-9 Gun Director. Bell Labs mathematician George Stibitz recommended using a relay-based calculator for the project. The result was the Relay Interpolator, later called the Bell Labs Model II. The Relay Interpolator used 440 relays and since it was programmable by paper tape, it was used for other applications following the war.

1944
Harvard Mark-I in use, 1944		Harvard Mark-1 is completed. Conceived by Harvard professor Howard Aiken, and designed and built by IBM, the Harvard Mark-1 was a room-sized, relay-based calculator. The machine had a fifty-foot long camshaft that synchronized the machine’s thousands of component parts. The Mark-1 was used to produce mathematical tables but was soon superseded by stored program computers.


The Colossus at Work At Bletchley Park		The first Colossus is operational at Bletchley Park. Designed by British engineer Tommy Flowers, the Colossus was designed to break the complex Lorenz ciphers used by the Nazis during WWII. A total of ten Colossi were delivered to Bletchley, each using 1,500 vacuum tubes and a series of pulleys transported continuous rolls of punched paper tape containing possible solutions to a particular code. Colossus reduced the time to break Lorenz messages from weeks to hours. The machine’s existence was not made public until the 1970s

1945
John von Neumann		John von Neumann wrote "First Draft of a Report on the EDVAC" in which he outlined the architecture of a stored-program computer. Electronic storage of programming information and data eliminated the need for the more clumsy methods of programming, such as punched paper tape — a concept that has characterized mainstream computer development since 1945. Hungarian-born von Neumann demonstrated prodigious expertise in hydrodynamics, ballistics, meteorology, game theory, statistics, and the use of mechanical devices for computation. After the war, he concentrated on the development of Princeton´s Institute for Advanced Studies computer and its copies around the world.

1946

ENIAC

In February, the public got its first glimpse of the ENIAC, a machine built by John Mauchly and J. Presper Eckert that improved by 1,000 times on the speed of its contemporaries.

Start of project:	1943
Completed:	1946
Programmed:	plug board and switches
Speed:	5,000 operations per second
Input/output:	cards, lights, switches, plugs
Floor space:	1,000 square feet
Project leaders:	John Mauchly and J. Presper Eckert.


AVIDAC		An inspiring summer school on computing at the University of Pennsylvania´s Moore School of Electrical Engineering stimulated construction of stored-program computers at universities and research institutions. This free, public set of lectures inspired the EDSAC, BINAC, and, later, IAS machine clones like the AVIDAC. Here, Warren Kelleher completes the wiring of the arithmetic unit components of the AVIDAC at Argonne National Laboratory. Robert Dennis installs the inter-unit wiring as James Woody Jr. adjusts the deflection control circuits of the memory unit.

1948

IBM´s SSEC

IBM´s Selective Sequence Electronic Calculator computed scientific data in public display near the company´s Manhattan headquarters. Before its decommissioning in 1952, the SSEC produced the moon-position tables used for plotting the course of the 1969 Apollo flight to the moon.

Speed:	50 multiplications per second
Input/output:	cards, punched tape
Memory type:	punched tape, vacuum tubes, relays
Technology:	20,000 relays, 12,500 vacuum tubes
Floor space:	25 feet by 40 feet
Project leader:	Wallace Eckert

1949

Wilkes with the EDSAC

Maurice Wilkes assembled the EDSAC, the first practical stored-program computer, at Cambridge University. His ideas grew out of the Moore School lectures he had attended three years earlier.

For programming the EDSAC, Wilkes established a library of short programs called subroutines stored on punched paper tapes.

Technology:	vacuum tubes
Memory:	1K words, 17 bits, mercury delay line
Speed:	714 operations per second

Manchester Mark I

The Manchester Mark I computer functioned as a complete system using the Williams tube for memory. This University machine became the prototype for Ferranti Corp.´s first computer.

Start of project:	1947
Completed:	1949
Add time:	1.8 microseconds
Input/output:	paper tape, teleprinter, switches
Memory size:	128 + 1024 40-digit words
Memory type:	cathode ray tube, magnetic drum
Technology:	1,300 vacuum tubes
Floor space:	medium room
Project leaders:	Frederick Williams and Tom Kilburn

1950
ERA 1101 drum memory		Engineering Research Associates of Minneapolis built the ERA 1101, the first commercially produced computer; the company´s first customer was the U.S. Navy. It held 1 million bits on its magnetic drum, the earliest magnetic storage devices. Drums registered information as magnetic pulses in tracks around a metal cylinder. Read/write heads both recorded and recovered the data. Drums eventually stored as many as 4,000 words and retrieved any one of them in as little as five-thousandths of a second.


SEAC		The National Bureau of Standards constructed the SEAC (Standards Eastern Automatic Computer) in Washington as a laboratory for testing components and systems for setting computer standards. The SEAC was the first computer to use all-diode logic, a technology more reliable than vacuum tubes, and the first stored-program computer completed in the United States. Magnetic tape in the external storage units (shown on the right of this photo) stored programming information, coded subroutines, numerical data, and output.


SWAC		The National Bureau of Standards completed its SWAC (Standards Western Automatic Computer) at the Institute for Numerical Analysis in Los Angeles. Rather than testing components like its companion, the SEAC, the SWAC had an objective of computing using already-developed technology.

Pilot ACE

Alan Turing´s philosophy directed design of Britain´s Pilot ACE at the National Physical Laboratory."We are trying to build a machine to do all kinds of different things simply by programming rather than by the addition of extra apparatus," Turing said at a symposium on large-scale digital calculating machinery in 1947 in Cambridge, Mass.

Start of project:	1948
Completed:	1950
Add time:	1.8 microseconds
Input/output:	cards
Memory size:	352 32-digit words
Memory type:	delay lines
Technology:	800 vacuum tubes
Floor space:	12 square feet
Project leader:	J. H. Wilkinson

1951

MIT Whirlwind

MIT´s Whirlwind debuted on Edward R. Murrow´s "See It Now" television series. Project director Jay Forrester described the computer as a "reliable operating system," running 35 hours a week at 90-percent utility using an electrostatic tube memory.

Start of project:	1945
Completed:	1951
Add time:	.05 microseconds
Input/output:	cathode ray tube, paper tape, magnetic tape
Memory size:	2048 16-digit words
Memory type:	cathode ray tube, magnetic drum, tape (1953 - core memory)
Technology:	4,500 vacuum tubes, 14,800 diodes
Floor space:	3,100 square feet
Project leaders:	Jay Forrester and Robert Everett


LEO		England´s first commercial computer, the Lyons Electronic Office, solved clerical problems. The president of Lyons Tea Co. had the computer, modeled after the EDSAC, built to solve the problem of daily scheduling production and delivery of cakes to the Lyons tea shops. After the success of the first LEO, Lyons went into business manufacturing computers to meet the growing need for data processing systems.

UNIVAC I

The UNIVAC I delivered to the U.S. Census Bureau was the first commercial computer to attract widespread public attention. Although manufactured by Remington Rand, the machine often was mistakenly referred to as the "IBM UNIVAC." Remington Rand eventually sold 46 machines at more than $1 million each.F.O.B. factory $750,000 plus $185,000 for a high speed printer.

Speed:	1,905 operations per second
Input/output:	magnetic tape, unityper, printer
Memory size:	1,000 12-digit words in delay lines
Memory type:	delay lines, magnetic tape
Technology:	serial vacuum tubes, delay lines, magnetic tape
Floor space:	943 cubic feet
Cost:	F.O.B. factory $750,000 plus $185,000 for a high speed printer
Project leaders:	J. Presper Eckert and John Mauchly

1952
Los Alamos MANIAC		John von Neumann´s IAS computer became operational at the Institute for Advanced Studies in Princeton, N.J. Contract obliged the builders to share their designs with other research institutes. This resulted in a number of clones: the MANIAC at Los Alamos Scientific Laboratory, the ILLIAC at the University of Illinois, the Johnniac at Rand Corp., the SILLIAC in Australia, and others.

1953
IBM 701		IBM shipped its first electronic computer, the 701. During three years of production, IBM sold 19 machines to research laboratories, aircraft companies, and the federal government.

1954
IBM 650		The IBM 650 magnetic drum calculator established itself as the first mass-produced computer, with the company selling 450 in one year. Spinning at 12,500 rpm, the 650´s magnetic data-storage drum allowed much faster access to stored material than drum memory machines.

1956
MIT TX0		MIT researchers built the TX-0, the first general-purpose, programmable computer built with transistors. For easy replacement, designers placed each transistor circuit inside a "bottle," similar to a vacuum tube. Constructed at MIT´s Lincoln Laboratory, the TX-0 moved to the MIT Research Laboratory of Electronics, where it hosted some early imaginative tests of programming, including a Western movie shown on TV, 3-D tic-tac-toe, and a maze in which mouse found martinis and became increasingly inebriated.

1958
SAGE operator station		SAGE — Semi-Automatic Ground Environment — linked hundreds of radar stations in the United States and Canada in the first large-scale computer communications network. An operator directed actions by touching a light gun to the screen. The air defense system operated on the AN/FSQ-7 computer (known as Whirlwind II during its development at MIT) as its central computer. Each computer used a full megawatt of power to drive its 55,000 vacuum tubes, 175,000 diodes and 13,000 transistors.


		Japan´s NEC built the country´s first electronic computer, the NEAC 1101.

1959
IBM STRETCH		IBM´s 7000 series mainframes were the company´s first transistorized computers. At the top of the line of computers — all of which emerged significantly faster and more dependable than vacuum tube machines — sat the 7030, also known as the "Stretch." Nine of the computers, which featured a 64-bit word and other innovations, were sold to national laboratories and other scientific users. L. R. Johnson first used the term "architecture" in describing the Stretch.

1960
DEC PDP-1		The precursor to the minicomputer, DEC´s PDP-1 sold for $120,000. One of 50 built, the average PDP-1 included with a cathode ray tube graphic display, needed no air conditioning and required only one operator. It´s large scope intrigued early hackers at MIT, who wrote the first computerized video game, SpaceWar!, for it. The SpaceWar! creators then used the game as a standard demonstration on all 50 computers.

1961
IBM 1401		According to Datamation magazine, IBM had an 81.2-percent share of the computer market in 1961, the year in which it introduced the 1400 Series. The 1401 mainframe, the first in the series, replaced the vacuum tube with smaller, more reliable transistors and used a magnetic core memory. Demand called for more than 12,000 of the 1401 computers, and the machine´s success made a strong case for using general-purpose computers rather than specialized systems.

1962
Wes Clark with LINC		The LINC (Laboratory Instrumentation Computer) offered the first real time laboratory data processing. Designed by Wesley Clark at Lincoln Laboratories, Digital Equipment Corp. later commercialized it as the LINC-8. Research faculty came to a workshop at MIT to build their own machines, most of which they used in biomedical studies. DEC supplied components.

1964
IBM System/360		IBM announced the System/360, a family of six mutually compatible computers and 40 peripherals that could work together. The initial investment of $5 billion was quickly returned as orders for the system climbed to 1,000 per month within two years. At the time IBM released the System/360, the company was making a transition from discrete transistors to integrated circuits, and its major source of revenue moved from punched-card equipment to electronic computer systems.


CDC 6600		CDC´s 6600 supercomputer, designed by Seymour Cray, performed up to 3 million instructions per second — a processing speed three times faster than that of its closest competitor, the IBM Stretch. The 6600 retained the distinction of being the fastest computer in the world until surpassed by its successor, the CDC 7600, in 1968. Part of the speed came from the computer´s design, which had 10 small computers, known as peripheral processors, funneling data to a large central processing unit.

1965
DEC PDP-8		Digital Equipment Corp. introduced the PDP-8, the first commercially successful minicomputer. The PDP-8 sold for $18,000, one-fifth the price of a small IBM 360 mainframe. The speed, small size, and reasonable cost enabled the PDP-8 to go into thousands of manufacturing plants, small businesses, and scientific laboratories.

1966
ILLIAC IV		The Department of Defense Advanced Research Projects Agency contracted with the University of Illinois to build a large parallel processing computer, the ILLIAC IV, which did not operate until 1972 at NASA´s Ames Research Center. The first large-scale array computer, the ILLIAC IV achieved a computation speed of 200 million instructions per second, about 300 million operations per second, and 1 billion bits per second of I/O transfer via a unique combination of parallel architecture and the overlapping or "pipe-lining" structure of its 64 processing elements. This photograph shows one of the ILLIAC´s 13 Burroughs disks, the debugging computer, the central unit, and the processing unit cabinet with a processing element.


HP-2115		Hewlett-Packard entered the general purpose computer business with its HP-2115 for computation, offering a computational power formerly found only in much larger computers. It supported a wide variety of languages, among them BASIC, ALGOL, and FORTRAN.

1968
Ed deCastro and Nova		Data General Corp., started by a group of engineers that had left Digital Equipment Corp., introduced the Nova, with 32 kilobytes of memory, for $8,000. In the photograph, Ed deCastro, president and founder of Data General, sits with a Nova minicomputer. The simple architecture of the Nova instruction set inspired Steve Wozniak´s Apple I board eight years later.


Apollo Guidance Computer		The Apollo Guidance Computer made its debut orbiting the Earth on Apollo 7. A year later, it steered Apollo 11 to the lunar surface. Astronauts communicated with the computer by punching two-digit codes and the appropriate syntactic category into the display and keyboard unit.

1971
Kenbak-1		The Kenbak-1, the first personal computer, advertised for $750 in Scientific American. Designed by John V. Blankenbaker using standard medium-scale and small-scale integrated circuits, the Kenbak-1 relied on switches for input and lights for output from its 256-byte memory. In 1973, after selling only 40 machines, Kenbak Corp. closed its doors.

1972
HP-35		Hewlett-Packard announced the HP-35 as "a fast, extremely accurate electronic slide rule" with a solid-state memory similar to that of a computer. The HP-35 distinguished itself from its competitors by its ability to perform a broad variety of logarithmic and trigonometric functions, to store more intermediate solutions for later use, and to accept and display entries in a form similar to standard scientific notation.

1973
TV Typewriter		The TV Typewriter, designed by Don Lancaster, provided the first display of alphanumeric information on an ordinary television set. It used $120 worth of electronics components, as outlined in the September 1973 issue of Radio Electronics. The original design included two memory boards and could generate and store 512 characters as 16 lines of 32 characters. A 90-minute cassette tape provided supplementary storage for about 100 pages of text.


Micral		The Micral was the earliest commercial, non-kit personal computer based on a micro-processor, the Intel 8008. Thi Truong developed the computer and Philippe Kahn the software. Truong, founder and president of the French company R2E, created the Micral as a replacement for minicomputers in situations that didn´t require high performance. Selling for $1,750, the Micral never penetrated the U.S. market. In 1979, Truong sold Micral to Bull.

1974
Xerox Alto		Researchers at the Xerox Palo Alto Research Center designed the Alto — the first work station with a built-in mouse for input. The Alto stored several files simultaneously in windows, offered menus and icons, and could link to a local area network. Although Xerox never sold the Alto commercially, it gave a number of them to universities. Engineers later incorporated its features into work stations and personal computers.


Scelbi 8H		Scelbi advertised its 8H computer, the first commercially advertised U.S. computer based on a microprocessor, Intel´s 8008. Scelbi aimed the 8H, available both in kit form and fully assembled, at scientific, electronic, and biological applications. It had 4 kilobytes of internal memory and a cassette tape, with both teletype and oscilloscope interfaces. In 1975, Scelbi introduced the 8B version with 16 kilobytes of memory for the business market. The company sold about 200 machines, losing $500 per unit.

1975
MITS Altair		The January edition of Popular Electronics featured the Altair 8800 computer kit, based on Intel´s 8080 microprocessor, on its cover. Within weeks of the computer´s debut, customers inundated the manufacturing company, MITS, with orders. Bill Gates and Paul Allen licensed BASIC as the software language for the Altair. Ed Roberts invented the 8800 — which sold for $297, or $395 with a case — and coined the term "personal computer." The machine came with 256 bytes of memory (expandable to 64K) and an open 100-line bus structure that evolved into the S-100 standard. In 1977, MITS sold out to Pertec, which continued producing Altairs through 1978.


Felsenstein´s VDM		The visual display module (VDM) prototype, designed in 1975 by Lee Felsenstein, marked the first implementation of a memory-mapped alphanumeric video display for personal computers. Introduced at the Altair Convention in Albuquerque in March 1976, the visual display module allowed use of personal computers for interactive games.


Tandem-16		Tandem computers tailored its Tandem-16, the first fault-tolerant computer, for online transaction processing. The banking industry rushed to adopt the machine, built to run during repair or expansion.

1976
Apple I		Steve Wozniak designed the Apple I, a single-board computer. With specifications in hand and an order for 100 machines at $500 each from the Byte Shop, he and Steve Jobs got their start in business. In this photograph of the Apple I board, the upper two rows are a video terminal and the lower two rows are the computer. The 6502 microprocessor in the white package sits on the lower right. About 200 of the machines sold before the company announced the Apple II as a complete computer.

Cray I

The Cray I made its name as the first commercially successful vector processor. The fastest machine of its day, its speed came partly from its shape, a C, which reduced the length of wires and thus the time signals needed to travel across them.

Project started:	1972
Project completed:	1976
Speed:	166 million floating-point operations per second
Size:	58 cubic feet
Weight:	5,300 lbs.
Technology:	Integrated circuit
Clock rate:	83 million cycles per second
Word length:	64-bit words
Instruction set:	128 instructions

1977
Commodore PET		The Commodore PET (Personal Electronic Transactor) — the first of several personal computers released in 1977 — came fully assembled and was straightforward to operate, with either 4 or 8 kilobytes of memory, two built-in cassette drives, and a membrane "chiclet" keyboard.


Apple II		The Apple II became an instant success when released in 1977 with its printed circuit motherboard, switching power supply, keyboard, case assembly, manual, game paddles, A/C powercord, and cassette tape with the computer game "Breakout." When hooked up to a color television set, the Apple II produced brilliant color graphics.


TRS-80		In the first month after its release, Tandy Radio Shack´s first desktop computer — the TRS-80 — sold 10,000 units, well more than the company´s projected sales of 3,000 units for one year. Priced at $599.95, the machine included a Z80 based microprocessor, a video display, 4 kilobytes of memory, BASIC, cassette storage, and easy-to-understand manuals that assumed no prior knowledge on the part of the consumer.

1978
VAX 11/780		The VAX 11/780 from Digital Equipment Corp. featured the ability to address up to 4.3 gigabytes of virtual memory, providing hundreds of times the capacity of most minicomputers.

1979
Advertisment for Atari 400 and 800 computers		Atari introduces the Model 400 and 800 Computer. Shortly after delivery of the Atari VCS game console, Atari designed two microcomputers with game capabilities: the Model 400 and Model 800. The two machines were built with the idea that the 400 would serve primarily as a game console while the 800 would be more of a home computer. Both sold well, though they had technical and marketing problems, and faced strong competition from the Apple II, Commodore PET, and TRS-80 computers.

1981
		IBM introduced its PC, igniting a fast growth of the personal computer market. The first PC ran on a 4.77 MHz Intel 8088 microprocessor and used Microsoft´s MS-DOS operating system.


Osborne I		Adam Osborne completed the first portable computer, the Osborne I, which weighed 24 pounds and cost $1,795. The price made the machine especially attractive, as it included software worth about $1,500. The machine featured a 5-inch display, 64 kilobytes of memory, a modem, and two 5 1/4-inch floppy disk drives. In April 1981, Byte Magazine Editor in Chief Chris Morgan mentioned the Osborne I in an article on "Future Trends in Personal Computing." He wrote: "I recently had an opportunity to see the Osborne I in action. I was impressed with it´s compactness: it will fit under an airplane seat. (Adam Osborne is currently seeking approval from the FAA to operate the unit on board a plane.) One quibble: the screen may be too small for some people´s taste."


Apollo DN100		Apollo Computer unveiled the first work station, its DN100, offering more power than some minicomputers at a fraction of the price. Apollo Computer and Sun Microsystems, another early entrant in the work station market, optimized their machines to run the computer-intensive graphics programs common in engineering.

1982
		The Cray XMP, first produced in this year, almost doubled the operating speed of competing machines with a parallel processing system that ran at 420 million floating-point operations per second, or megaflops. Arranging two Crays to work together on different parts of the same problem achieved the faster speed. Defense and scientific research institutes also heavily used Crays.


Early Publicity still for the Commodore 64		Commodore introduces the Commodore 64. The C64, as it was better known, sold for $595, came with 64KB of RAM and featured impressive graphics. Thousands of software titles were released over the lifespan of the C64. By the time the C64 was discontinued in 1993, it had sold more than 22 million units and is recognized by the 2006 Guinness Book of World Records as the greatest selling single computer model of all time.

1983
		Apple introduced its Lisa. The first personal computer with a graphical user interface, its development was central in the move to such systems for personal computers. The Lisa´s sloth and high price ($10,000) led to its ultimate failure. The Lisa ran on a Motorola 68000 microprocessor and came equipped with 1 megabyte of RAM, a 12-inch black-and-white monitor, dual 5 1/4-inch floppy disk drives and a 5 megabyte Profile hard drive. The Xerox Star — which included a system called Smalltalk that involved a mouse, windows, and pop-up menus — inspired the Lisa´s designers.


Compaq PC clone		Compaq Computer Corp. introduced first PC clone that used the same software as the IBM PC. With the success of the clone, Compaq recorded first-year sales of $111 million, the most ever by an American business in a single year. With the introduction of its PC clone, Compaq launched a market for IBM-compatible computers that by 1996 had achieved a 83-percent share of the personal computer market. Designers reverse-engineered the Compaq clone, giving it nearly 100-percent compatibility with the IBM.

1984
Apple Macintosh		Apple Computer launched the Macintosh, the first successful mouse-driven computer with a graphic user interface, with a single $1.5 million commercial during the 1984 Super Bowl. Based on the Motorola 68000 microprocessor, the Macintosh included many of the Lisa´s features at a much more affordable price: $2,500. Apple´s commercial played on the theme of George Orwell´s "1984" and featured the destruction of Big Brother with the power of personal computing found in a Macintosh. Applications that came as part of the package included MacPaint, which made use of the mouse, and MacWrite, which demonstrated WYSIWYG (What You See Is What You Get) word processing.


IBM PC Jr.		IBM released its PC Jr. and PC-AT. The PC Jr. failed, but the PC-AT, several times faster than original PC and based on the Intel 80286 chip, claimed success with its notable increases in performance and storage capacity, all for about $4,000. It also included more RAM and accommodated high-density 1.2-megabyte 5 1/4-inch floppy disks.

1985
Amiga 1000 with Seiko Music Keyboard		The Amiga 1000 is released. Commodore’s Amiga 1000 sold for $1,295 dollars (without monitor) and had audio and video capabilities beyond those found in most other personal computers. It developed a very loyal following and add-on components allowed it to be upgraded easily. The inside of the case is engraved with the signatures of the Amiga designers, including Jay Miner as well as the paw print of his dog Mitchy.

1986
Connection Machine		Daniel Hillis of Thinking Machines Corp. moved artificial intelligence a step forward when he developed the controversial concept of massive parallelism in the Connection Machine. The machine used up to 65,536 processors and could complete several billion operations per second. Each processor had its own small memory linked with others through a flexible network that users could alter by reprogramming rather than rewiring. The machine´s system of connections and switches let processors broadcast information and requests for help to other processors in a simulation of brainlike associative recall. Using this system, the machine could work faster than any other at the time on a problem that could be parceled out among the many processors.


		IBM and MIPS released the first RISC-based workstations, the PC/RT and R2000-based systems. Reduced instruction set computers grew out of the observation that the simplest 20 percent of a computer´s instruction set does 80 percent of the work, including most base operations such as add, load from memory, and store in memory. The IBM PC-RT had 1 megabyte of RAM, a 1.2-megabyte floppy disk drive, and a 40-megabyte hard drive. It performed 2 million instructions per second, but other RISC-based computers worked significantly faster.

1987
IBM PS/2		IBM introduced its PS/2 machines, which made the 3 1/2-inch floppy disk drive and video graphics array standard for IBM computers. The first IBMs to include Intel´s 80386 chip, the company had shipped more than 1 million units by the end of the year. IBM released a new operating system, OS/2, at the same time, allowing the use of a mouse with IBMs for the first time.

1988
		Apple cofounder Steve Jobs, who left Apple to form his own company, unveiled the NeXT. The computer he created failed but was recognized as an important innovation. At a base price of $6,500, the NeXT ran too slowly to be popular. The significance of the NeXT rested in its place as the first personal computer to incorporate a drive for an optical storage disk, a built-in digital signal processor that allowed voice recognition, and object-oriented languages to simplify programming. The NeXT offered Motorola 68030 microprocessors, 8 megabytes of RAM, and a 256-megabyte read/write optical disk storage.

Most Popular Computer Facts(Learn for knowledge)..

1. Bill Gates' house was designed using a Macintosh computer.

2. TYPEWRITER is the longest word that can be made using the letters only on one row of the keyboard.

3. While it took the radio 38 years, and the television a short 13 years, it took the World Wide Web only 4 years to reach 50 million users.

4. There are approximately 1,319,872,109 people on the Internet.

5. "Stewardesses" is the longest word that is typed with only the left hand.

More Computer Facts

1. On an average work day, a typist's fingers travel 12.6 miles.

2. The Dvorak keyboard is more efficient than QWERTY. 20 times faster, in fact.

3. TYPEWRITER is the longest word that can be made using the letters only on one row of the keyboard.

4. On eBay, there are an average of $680 worth of transactions each second.

5. "Stewardesses" is the longest word that is typed with only the left hand.

6. 80% of all pictures on the internet are of naked women

7. In the 1980s, an IBM computer wasn't considered 100 percent compatible unless it could run Microsoft Flight Simulator*.

8. The world's first computer, called the Z1, was invented by Konrad Zuse in 1936. His next invention, the Z2 was finished in 1939 and was the first fully functioning electro-mechanical computer.

9. The first computer mouse was invented by Doug Engelbart in around 1964 and was made of wood.

10. Domain names are being registered at a rate of more than one million names every month.

11. There are approximately 1.06 billion instant messaging accounts worldwide.

12. The first banner advertising was used in 1994.

13. E-mail has been around longer than the World Wide Web.

14. The average computer user blinks 7 times a minute, less than half the normal rate of 20.

15. One of every 8 married couples in the US last year met online.

16. The average 21 year old has spent 5,000 hours playing video games, has exchanged 250,000 e-mails, instant and text messages and has spent 10,000 hours on the mobile phone.

17. By the year 2012 there will be approximately 17 billion devices connected to the Internet.

18. MySpace reports over 110 million registered users. Were it a country, it would be the tenth largest, just behind Mexico.

19. While it took the radio 38 years, and the television a short 13 years, it took the World Wide Web only 4 years to reach 50 million users.

20. There are approximately 1,319,872,109 people on the Internet.

21. For every 'normal' webpage, there are five porn pages.

22. Bill Gates' house was designed using a Macintosh computer.

23. The first domain name ever registered was Symbolics.com.

24. Another name for a Microsoft Windows tutorial is 'Crash Course'!

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